The anatomical and physiological maturation of the cells of the avian ciliary ganglion will be studied both following removal of the peripheral target organs and also following removal of the afferent input. Development of functional motor innervation in the chick limb is also being studied by electrical stimulation of spinal nerves in isolated spinal cord - hind limb preparations. The sequence of synaptogenesis in the spinal cord is also under study by physiological techniques. The mechanism of suppression of foreign synapses resulting from crossed innervation, following regneration of the proper nerve is under study in fish and frog extraocular muscles.